// script.aculo.us dragdrop.js v1.8.1, Thu Jan 03 22:07:12 -0500 2008
// Copyright (c) 2005-2007 Thomas Fuchs (http://script.aculo.us, http://mir.aculo.us)
//           (c) 2005-2007 Sammi Williams (http://www.oriontransfer.co.nz, sammi@oriontransfer.co.nz)
//
// script.aculo.us is freely distributable under the terms of an MIT-style license.
// For details, see the script.aculo.us web site: http://script.aculo.us/
if (Object.isUndefined(Effect)) throw ("dragdrop.js requires including script.aculo.us' effects.js library");

var Droppables = {
	drops: [],

	remove: function(element) {
		this.drops = this.drops.reject(function(d) {
			return d.element == $(element)
		});
	},

	add: function(element) {
		element = $(element);
		var options = Object.extend({
			greedy: true,
			hoverclass: null,
			tree: false
		},
		arguments[1] || {});

		 // cache containers
		if (options.containment) {
			options._containers = [];
			var containment = options.containment;
			if (Object.isArray(containment)) {
				containment.each(function(c) {
					options._containers.push($(c))
				});
			} else {
				options._containers.push($(containment));
			}
		}

		if (options.accept) options.accept = [options.accept].flatten();

		Element.makePositioned(element); // fix IE
		options.element = element;

		this.drops.push(options);
	},

	findDeepestChild: function(drops) {
		deepest = drops[0];

		for (i = 1; i < drops.length; ++i) if (Element.isParent(drops[i].element, deepest.element)) deepest = drops[i];

		return deepest;
	},

	isContained: function(element, drop) {
		var containmentNode;
		if (drop.tree) {
			containmentNode = element.treeNode;
		} else {
			containmentNode = element.parentNode;
		}
		return drop._containers.detect(function(c) {
			return containmentNode == c
		});
	},

	isAffected: function(point, element, drop) {
		return ((drop.element != element) && ((!drop._containers) || this.isContained(element, drop)) && ((!drop.accept) || (Element.classNames(element).detect(function(v) {
			return drop.accept.include(v)
		}))) && Position.within(drop.element, point[0], point[1]));
	},

	deactivate: function(drop) {
		if (drop.hoverclass) Element.removeClassName(drop.element, drop.hoverclass);
		this.last_active = null;
	},

	activate: function(drop) {
		if (drop.hoverclass) Element.addClassName(drop.element, drop.hoverclass);
		this.last_active = drop;
	},

	show: function(point, element) {
		if (!this.drops.length) return;
		var drop,affected = [];
		
		this.drops.each(function(drop) {
			if (Droppables.isAffected(point, element, drop)) affected.push(drop);
		});

		if (affected.length > 0) drop = Droppables.findDeepestChild(affected);

		if (this.last_active && this.last_active != drop) this.deactivate(this.last_active);
		if (drop) {
			Position.within(drop.element, point[0], point[1]);
			if (drop.onHover) drop.onHover(element, drop.element, Position.overlap(drop.overlap, drop.element));

			if (drop != this.last_active) Droppables.activate(drop);
		}
	},

	fire: function(event, element) {
		if (!this.last_active) return;
		Position.prepare();

		if (this.isAffected([Event.pointerX(event), Event.pointerY(event)], element, this.last_active)) if (this.last_active.onDrop) {
			this.last_active.onDrop(element, this.last_active.element, event);
			return true;
		}
	},

	reset: function() {
		if (this.last_active) this.deactivate(this.last_active);
	}
}

var Draggables = {
	drags: [],
	observers: [],

	register: function(draggable) {
		if (this.drags.length == 0) {
			this.eventMouseUp = this.endDrag.bindAsEventListener(this);
			this.eventMouseMove = this.updateDrag.bindAsEventListener(this);
			this.eventKeypress = this.keyPress.bindAsEventListener(this);

			Event.observe(document, "mouseup", this.eventMouseUp);
			Event.observe(document, "mousemove", this.eventMouseMove);
			Event.observe(document, "keypress", this.eventKeypress);
		}
		this.drags.push(draggable);
	},

	unregister: function(draggable) {
		this.drags = this.drags.reject(function(d) {
			return d == draggable
		});
		if (this.drags.length == 0) {
			Event.stopObserving(document, "mouseup", this.eventMouseUp);
			Event.stopObserving(document, "mousemove", this.eventMouseMove);
			Event.stopObserving(document, "keypress", this.eventKeypress);
		}
	},

	activate: function(draggable) {
		if (draggable.options.delay) {
			this._timeout = setTimeout(function() {
				Draggables._timeout = null;
				window.focus();
				Draggables.activeDraggable = draggable;
			}.bind(this), draggable.options.delay);
		} else {
			window.focus(); // allows keypress events if window isn't currently focused, fails for Safari
			this.activeDraggable = draggable;
		}
	},

	deactivate: function() {
		this.activeDraggable = null;
	},

	updateDrag: function(event) {
		if (!this.activeDraggable) return;
		var pointer = [Event.pointerX(event), Event.pointerY(event)];
		 // Mozilla-based browsers fire successive mousemove events with
		 // the same coordinates, prevent needless redrawing (moz bug?)
		if (this._lastPointer && (this._lastPointer.inspect() == pointer.inspect())) return;
		this._lastPointer = pointer;

		this.activeDraggable.updateDrag(event, pointer);
	},

	endDrag: function(event) {
		if (this._timeout) {
			clearTimeout(this._timeout);
			this._timeout = null;
		}
		if (!this.activeDraggable) return;
		this._lastPointer = null;
		this.activeDraggable.endDrag(event);
		this.activeDraggable = null;
	},

	keyPress: function(event) {
		if (this.activeDraggable) this.activeDraggable.keyPress(event);
	},

	addObserver: function(observer) {
		this.observers.push(observer);
		this._cacheObserverCallbacks();
	},

	removeObserver: function(element) { // element instead of observer fixes mem leaks
		this.observers = this.observers.reject(function(o) {
			return o.element == element
		});
		this._cacheObserverCallbacks();
	},

	notify: function(eventName, draggable, event) { // 'onStart', 'onEnd', 'onDrag'
		if (this[eventName + 'Count'] > 0) this.observers.each(function(o) {
			if (o[eventName]) o[eventName](eventName, draggable, event);
		});
		if (draggable.options[eventName]) draggable.options[eventName](draggable, event);
	},

	_cacheObserverCallbacks: function() { ['onStart', 'onEnd', 'onDrag'].each(function(eventName) {
			Draggables[eventName + 'Count'] = Draggables.observers.select(function(o) {
				return o[eventName];
			}).length;
		});
	}
}

/*--------------------------------------------------------------------------*/

var Draggable = Class.create({
	initialize: function(element) {
		var defaults = {
			handle: false,
			reverteffect: function(element, top_offset, left_offset) {
				var dur = Math.sqrt(Math.abs(top_offset ^ 2) + Math.abs(left_offset ^ 2)) * 0.02;
				new Effect.Move(element, {
					x: -left_offset,
					y: -top_offset,
					duration: dur,
					queue: {
						scope: '_draggable',
						position: 'end'
					}
				});
			},
			endeffect: function(element) {
				var toOpacity = Object.isNumber(element._opacity) ? element._opacity: 1.0;
				new Effect.Opacity(element, {
					duration: 0.2,
					from: 0.7,
					to: toOpacity,
					queue: {
						scope: '_draggable',
						position: 'end'
					},
					afterFinish: function() {
						Draggable._dragging[element] = false
					}
				});
			},
			zindex: 1000,
			revert: false,
			quiet: false,
			scroll: false,
			scrollSensitivity: 20,
			scrollSpeed: 15,
			snap: false,
			 // false, or xy or [x,y] or function(x,y){ return [x,y] }
			delay: 0
		};

		if (!arguments[1] || Object.isUndefined(arguments[1].endeffect)) Object.extend(defaults, {
			starteffect: function(element) {
				element._opacity = Element.getOpacity(element);
				Draggable._dragging[element] = true;
				new Effect.Opacity(element, {
					duration: 0.2,
					from: element._opacity,
					to: 0.7
				});
			}
		});

		var options = Object.extend(defaults, arguments[1] || {});

		this.element = $(element);


		if (options.handle && Object.isString(options.handle)) this.handle = this.element.down('.' + options.handle, 0);

		if (!this.handle) this.handle = $(options.handle);
		if (!this.handle) this.handle = this.element;

		if (options.scroll && !options.scroll.scrollTo && !options.scroll.outerHTML) {
			options.scroll = $(options.scroll);
			this._isScrollChild = Element.childOf(this.element, options.scroll);
		}

		Element.makePositioned(this.element); // fix IE
		this.options = options;
		this.dragging = false;

		this.eventMouseDown = this.initDrag.bindAsEventListener(this);
		Event.observe(this.handle, "mousedown", this.eventMouseDown);

		Draggables.register(this);
	},

	destroy: function() {
		Event.stopObserving(this.handle, "mousedown", this.eventMouseDown);
		Draggables.unregister(this);
	},

	currentDelta: function() {
		return ([parseInt(Element.getStyle(this.element, 'left') || '0'), parseInt(Element.getStyle(this.element, 'top') || '0')]);
	},

	initDrag: function(event) {
		if (!Object.isUndefined(Draggable._dragging[this.element]) && Draggable._dragging[this.element]) return;
		if (Event.isLeftClick(event)) {
			 // abort on form elements, fixes a Firefox issue
			var src = Event.element(event);
			if ((tag_name = src.tagName.toUpperCase()) && (tag_name == 'INPUT' || tag_name == 'SELECT' || tag_name == 'OPTION' || tag_name == 'BUTTON' || tag_name == 'TEXTAREA')) return;

			var pointer = [Event.pointerX(event), Event.pointerY(event)];
			var pos = Position.cumulativeOffset(this.element);
			this.offset = [0, 1].map(function(i) {
				return (pointer[i] - pos[i])
			});

			Draggables.activate(this);
			Event.stop(event);
		}
	},

	startDrag: function(event) {
		this.dragging = true;
		if (!this.delta) this.delta = this.currentDelta();

		if (this.options.zindex) {
			this.originalZ = parseInt(Element.getStyle(this.element, 'z-index') || 0);
			this.element.style.zIndex = this.options.zindex;
		}

		if (this.options.ghosting) {
			this._clone = this.element.cloneNode(true);
			this.element._originallyAbsolute = (this.element.getStyle('position') == 'absolute');
			if (!this.element._originallyAbsolute) Position.absolutize(this.element);
			this.element.parentNode.insertBefore(this._clone, this.element);
		}

		if (this.options.scroll) {
			if (this.options.scroll == window) {
				var where = this._getWindowScroll(this.options.scroll);
				this.originalScrollLeft = where.left;
				this.originalScrollTop = where.top;
			} else {
				this.originalScrollLeft = this.options.scroll.scrollLeft;
				this.originalScrollTop = this.options.scroll.scrollTop;
			}
		}

		Draggables.notify('onStart', this, event);

		if (this.options.starteffect) this.options.starteffect(this.element);
	},

	updateDrag: function(event, pointer) {

		if (!this.dragging) this.startDrag(event);
		

		if (!this.options.quiet) {
			Position.prepare();
			Droppables.show(pointer, this.element);
		}

		Draggables.notify('onDrag', this, event);

		this.draw(pointer);
		if (this.options.change) this.options.change(this);

		if (this.options.scroll) {
			this.stopScrolling();

			var p;
			if (this.options.scroll == window) {
				with(this._getWindowScroll(this.options.scroll)) {
					p = [left, top, left + width, top + height];
				}
			} else {
				p = Position.page(this.options.scroll);
				p[0] += this.options.scroll.scrollLeft + Position.deltaX;
				p[1] += this.options.scroll.scrollTop + Position.deltaY;
				p.push(p[0] + this.options.scroll.offsetWidth);
				p.push(p[1] + this.options.scroll.offsetHeight);
			}
			var speed = [0, 0];
			if (pointer[0] < (p[0] + this.options.scrollSensitivity)) speed[0] = pointer[0] - (p[0] + this.options.scrollSensitivity);
			if (pointer[1] < (p[1] + this.options.scrollSensitivity)) speed[1] = pointer[1] - (p[1] + this.options.scrollSensitivity);
			if (pointer[0] > (p[2] - this.options.scrollSensitivity)) speed[0] = pointer[0] - (p[2] - this.options.scrollSensitivity);
			if (pointer[1] > (p[3] - this.options.scrollSensitivity)) speed[1] = pointer[1] - (p[3] - this.options.scrollSensitivity);
			this.startScrolling(speed);
		}

		 // fix AppleWebKit rendering
		if (Prototype.Browser.WebKit) window.scrollBy(0, 0);

		Event.stop(event);
	},

	finishDrag: function(event, success) {

		this.dragging = false;
		
		if (this.options.quiet) {
			Position.prepare();
			var pointer = [Event.pointerX(event), Event.pointerY(event)];
			Droppables.show(pointer, this.element);
		}

		if (this.options.ghosting) {
			if (!this.element._originallyAbsolute) Position.relativize(this.element);
			delete this.element._originallyAbsolute;
			Element.remove(this._clone);
			this._clone = null;
		}

		var dropped = false;
		if (success) {
			dropped = Droppables.fire(event, this.element);
			if (!dropped) dropped = false;
		}
		if (dropped && this.options.onDropped) this.options.onDropped(this.element);
		Draggables.notify('onEnd', this, event);

		
		
		////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
		/*ances = $(this.element).ancestors();
		level = ((ances.length-2)/2);
		if (level > 3) {//maxLevel
			this.options.revert = true;
		}*/
		////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
		//else {
			var revert = this.options.revert;
			if (revert && Object.isFunction(revert)) revert = revert(this.element);
			var d = this.currentDelta();
			if (revert && this.options.reverteffect) {
				if (dropped == 0 || revert != 'failure') this.options.reverteffect(this.element, d[1] - this.delta[1], d[0] - this.delta[0]);
			}
			else this.delta = d;
		//}
		if (this.options.zindex) this.element.style.zIndex = this.originalZ;
		if (this.options.endeffect) this.options.endeffect(this.element);

		Draggables.deactivate(this);
		Droppables.reset();
	},

	keyPress: function(event) {
		if (event.keyCode != Event.KEY_ESC) return;
		this.finishDrag(event, false);
		Event.stop(event);
	},

	endDrag: function(event) {
		if (!this.dragging) return;
		this.stopScrolling();
		this.finishDrag(event, true);
		Event.stop(event);
	},

	draw: function(point) {
		var pos = Position.cumulativeOffset(this.element);
		if (this.options.ghosting) {
			var r = Position.realOffset(this.element);
			pos[0] += r[0] - Position.deltaX;
			pos[1] += r[1] - Position.deltaY;
		}

		var d = this.currentDelta();
		pos[0] -= d[0];
		pos[1] -= d[1];

		if (this.options.scroll && (this.options.scroll != window && this._isScrollChild)) {
			pos[0] -= this.options.scroll.scrollLeft - this.originalScrollLeft;
			pos[1] -= this.options.scroll.scrollTop - this.originalScrollTop;
		}

		var p = [0, 1].map(function(i) {
			return (point[i] - pos[i] - this.offset[i])
		}.bind(this));

		if (this.options.snap) {
			if (Object.isFunction(this.options.snap)) {
				p = this.options.snap(p[0], p[1], this);
			} else {
				if (Object.isArray(this.options.snap)) {
					p = p.map(function(v, i) {
						return (v / this.options.snap[i]).round() * this.options.snap[i]
					}.bind(this))
				} else {
					p = p.map(function(v) {
						return (v / this.options.snap).round() * this.options.snap
					}.bind(this))
				}
			}
		}

		var style = this.element.style;
		if ((!this.options.constraint) || (this.options.constraint == 'horizontal')) style.left = p[0] + "px";
		if ((!this.options.constraint) || (this.options.constraint == 'vertical')) style.top = p[1] + "px";

		if (style.visibility == "hidden") style.visibility = ""; // fix gecko rendering
	},

	stopScrolling: function() {
		if (this.scrollInterval) {
			clearInterval(this.scrollInterval);
			this.scrollInterval = null;
			Draggables._lastScrollPointer = null;
		}
	},

	startScrolling: function(speed) {
		if (! (speed[0] || speed[1])) return;
		this.scrollSpeed = [speed[0] * this.options.scrollSpeed, speed[1] * this.options.scrollSpeed];
		this.lastScrolled = new Date();
		this.scrollInterval = setInterval(this.scroll.bind(this), 10);
	},

	scroll: function() {
		var current = new Date();
		var delta = current - this.lastScrolled;
		this.lastScrolled = current;
		if (this.options.scroll == window) {
			with(this._getWindowScroll(this.options.scroll)) {
				if (this.scrollSpeed[0] || this.scrollSpeed[1]) {
					var d = delta / 1000;
					this.options.scroll.scrollTo(left + d * this.scrollSpeed[0], top + d * this.scrollSpeed[1]);
				}
			}
		} else {
			this.options.scroll.scrollLeft += this.scrollSpeed[0] * delta / 1000;
			this.options.scroll.scrollTop += this.scrollSpeed[1] * delta / 1000;
		}

		Position.prepare();
		Droppables.show(Draggables._lastPointer, this.element);
		Draggables.notify('onDrag', this);
		if (this._isScrollChild) {
			Draggables._lastScrollPointer = Draggables._lastScrollPointer || $A(Draggables._lastPointer);
			Draggables._lastScrollPointer[0] += this.scrollSpeed[0] * delta / 1000;
			Draggables._lastScrollPointer[1] += this.scrollSpeed[1] * delta / 1000;
			if (Draggables._lastScrollPointer[0] < 0) Draggables._lastScrollPointer[0] = 0;
			if (Draggables._lastScrollPointer[1] < 0) Draggables._lastScrollPointer[1] = 0;
			this.draw(Draggables._lastScrollPointer);
		}

		if (this.options.change) this.options.change(this);
	},

	_getWindowScroll: function(w) {
		var T,
		L,
		W,
		H;
		with(w.document) {
			if (w.document.documentElement && documentElement.scrollTop) {
				T = documentElement.scrollTop;
				L = documentElement.scrollLeft;
			} else if (w.document.body) {
				T = body.scrollTop;
				L = body.scrollLeft;
			}
			if (w.innerWidth) {
				W = w.innerWidth;
				H = w.innerHeight;
			} else if (w.document.documentElement && documentElement.clientWidth) {
				W = documentElement.clientWidth;
				H = documentElement.clientHeight;
			} else {
				W = body.offsetWidth;
				H = body.offsetHeight
			}
		}
		return {
			top: T,
			left: L,
			width: W,
			height: H
		};
	}
});

Draggable._dragging = {};

/*--------------------------------------------------------------------------*/

var SortableObserver = Class.create({
	initialize: function(element, observer) {
		this.element = $(element);
		this.observer = observer;
		this.lastValue = Sortable.serialize(this.element);
	},

	onStart: function() {
		this.lastValue = Sortable.serialize(this.element);
	},

	onEnd: function() {
		Sortable.unmark();
		if (this.lastValue != Sortable.serialize(this.element)) this.observer(this.element)
	}
});

var Sortable = {
	SERIALIZE_RULE: /^[^_\-](?:[A-Za-z0-9\-\_]*)[_](.*)$/,

	sortables: {},

	_findRootElement: function(element) {
		while (element.tagName.toUpperCase() != "BODY") {
			if (element.id && Sortable.sortables[element.id]) return element;
			element = element.parentNode;
		}
	},

	options: function(element) {
		element = Sortable._findRootElement($(element));
		if (!element) return;
		return Sortable.sortables[element.id];
	},

	destroy: function(element) {
		var s = Sortable.options(element);

		if (s) {
			Draggables.removeObserver(s.element);
			s.droppables.each(function(d) {
				Droppables.remove(d)
			});
			s.draggables.invoke('destroy');

			delete Sortable.sortables[s.element.id];
		}
	},

	create: function(element) {
		element = $(element);
		var options = Object.extend({
			element: element,
			tag: 'li',
			 // assumes li children, override with tag: 'tagname'
			dropOnEmpty: false,
			tree: false,
			treeTag: 'ul',
			overlap: 'vertical',
			 // one of 'vertical', 'horizontal'
			constraint: 'vertical',
			 // one of 'vertical', 'horizontal', false
			containment: element,
			 // also takes array of elements (or id's); or false
			handle: false,
			 // or a CSS class
			only: false,
			delay: 0,
			hoverclass: null,
			ghosting: false,
			quiet: false,
			scroll: false,
			scrollSensitivity: 20,
			scrollSpeed: 15,
			format: this.SERIALIZE_RULE,

			 // these take arrays of elements or ids and can be
			 // used for better initialization performance
			elements: false,
			handles: false,

			onChange: Prototype.emptyFunction,
			onUpdate: Prototype.emptyFunction
		},
		arguments[1] || {});

		 // clear any old sortable with same element
		this.destroy(element);

		 // build options for the draggables
		var options_for_draggable = {
			revert: true,
			quiet: options.quiet,
			scroll: options.scroll,
			scrollSpeed: options.scrollSpeed,
			scrollSensitivity: options.scrollSensitivity,
			delay: options.delay,
			ghosting: options.ghosting,
			constraint: options.constraint,
			handle: options.handle
		};

		if (options.starteffect) options_for_draggable.starteffect = options.starteffect;

		if (options.reverteffect) options_for_draggable.reverteffect = options.reverteffect;
		else if (options.ghosting) options_for_draggable.reverteffect = function(element) {
			element.style.top = 0;
			element.style.left = 0;
		};

		if (options.endeffect) options_for_draggable.endeffect = options.endeffect;

		if (options.zindex) options_for_draggable.zindex = options.zindex;

		 // build options for the droppables
		var options_for_droppable = {
			overlap: options.overlap,
			containment: options.containment,
			tree: options.tree,
			hoverclass: options.hoverclass,
			onHover: Sortable.onHover
		}

		var options_for_tree = {
			onHover: Sortable.onEmptyHover,
			overlap: options.overlap,
			containment: options.containment,
			hoverclass: options.hoverclass
		}

		 // fix for gecko engine
		Element.cleanWhitespace(element);

		options.draggables = [];
		options.droppables = [];

		 // drop on empty handling
		if (options.dropOnEmpty || options.tree) {
			Droppables.add(element, options_for_tree);
			options.droppables.push(element);
		}

		(options.elements || this.findElements(element, options) || []).each(function(e, i) {
			var handle = options.handles ? $(options.handles[i]) : (options.handle ? $(e).select('.' + options.handle)[0] : e);
			options.draggables.push(new Draggable(e, Object.extend(options_for_draggable, {
				handle: handle
			})));
			Droppables.add(e, options_for_droppable);
			if (options.tree) e.treeNode = element;
			options.droppables.push(e);
		});

		if (options.tree) { (Sortable.findTreeElements(element, options) || []).each(function(e) {
				Droppables.add(e, options_for_tree);
				e.treeNode = element;
				options.droppables.push(e);
			});
		}

		 // keep reference
		this.sortables[element.id] = options;

		 // for onupdate
		Draggables.addObserver(new SortableObserver(element, options.onUpdate));

	},

	 // return all suitable-for-sortable elements in a guaranteed order
	findElements: function(element, options) {
		return Element.findChildren(element, options.only, options.tree ? true: false, options.tag);
	},

	findTreeElements: function(element, options) {
		return Element.findChildren(element, options.only, options.tree ? true: false, options.treeTag);
	},

	onHover: function(element, dropon, overlap) {
		if (Element.isParent(dropon, element)) return;	
		if (overlap > .33 && overlap < .66 && Sortable.options(dropon).tree) {
			return;
		} else if (overlap > 0.5) {
			Sortable.mark(dropon, 'before');
			if (dropon.previousSibling != element) {
				var oldParentNode = element.parentNode;
				element.style.visibility = "hidden"; // fix gecko rendering
				dropon.parentNode.insertBefore(element, dropon);
				if (dropon.parentNode != oldParentNode) Sortable.options(oldParentNode).onChange(element);
				Sortable.options(dropon.parentNode).onChange(element);
			}
		} else {
			Sortable.mark(dropon, 'after');
			var nextElement = dropon.nextSibling || null;
			if (nextElement != element) {
				var oldParentNode = element.parentNode;
				element.style.visibility = "hidden"; // fix gecko rendering
				dropon.parentNode.insertBefore(element, nextElement);
				if (dropon.parentNode != oldParentNode) Sortable.options(oldParentNode).onChange(element);
				Sortable.options(dropon.parentNode).onChange(element);
			}
		}
	},

	onEmptyHover: function(element, dropon, overlap) {
		var oldParentNode = element.parentNode;
		var droponOptions = Sortable.options(dropon);

		if (!Element.isParent(dropon, element)) {
			var index;

			var children = Sortable.findElements(dropon, {
				tag: droponOptions.tag,
				only: droponOptions.only
			});
			var child = null;

			if (children) {
				var offset = Element.offsetSize(dropon, droponOptions.overlap) * (1.0 - overlap);

				for (index = 0; index < children.length; index += 1) {
					if (offset - Element.offsetSize(children[index], droponOptions.overlap) >= 0) {
						offset -= Element.offsetSize(children[index], droponOptions.overlap);
					} else if (offset - (Element.offsetSize(children[index], droponOptions.overlap) / 2) >= 0) {
						child = index + 1 < children.length ? children[index + 1] : null;
						break;
					} else {
						child = children[index];
						break;
					}
				}
			}

			dropon.insertBefore(element, child);

			Sortable.options(oldParentNode).onChange(element);
			droponOptions.onChange(element);
		}
	},

	unmark: function() {
		if (Sortable._marker) Sortable._marker.hide();
	},

	mark: function(dropon, position) {
		// mark on ghosting only
		var sortable = Sortable.options(dropon.parentNode);
		if (sortable && !sortable.ghosting) return;

		if (!Sortable._marker) {
			Sortable._marker = ($('dropmarker') || Element.extend(document.createElement('li'))).hide().addClassName('dropmarker').setStyle({
				position: 'absolute'
			});
			document.getElementsByTagName("body").item(0).appendChild(Sortable._marker);
		}
		var offsets = Position.cumulativeOffset(dropon);
		Sortable._marker.setStyle({
			left: offsets[0] + 'px',
			top: offsets[1] + 'px'
		});

		if (position == 'after') if (sortable.overlap == 'horizontal') Sortable._marker.setStyle({
			left: (offsets[0] + dropon.clientWidth) + 'px'
		});
		else Sortable._marker.setStyle({
			top: (offsets[1] + dropon.clientHeight) + 'px'
		});

		Sortable._marker.show();
	},

	_tree: function(element, options, parent) {
		var children = Sortable.findElements(element, options) || [];

		for (var i = 0; i < children.length; ++i) {
			var match = children[i].id.match(options.format);

			if (!match) continue;

			var child = {
				id: encodeURIComponent(match ? match[1] : null),
				element: element,
				parent: parent,
				children: [],
				position: parent.children.length,
				container: $(children[i]).down(options.treeTag)
			}

			/* Get the element containing the children and recurse over it */
			if (child.container) this._tree(child.container, options, child)

			 parent.children.push(child);
		}

		return parent;
	},

	tree: function(element) {
		element = $(element);
		var sortableOptions = this.options(element);
		var options = Object.extend({
			tag: sortableOptions.tag,
			treeTag: sortableOptions.treeTag,
			only: sortableOptions.only,
			name: element.id,
			format: sortableOptions.format
		},
		arguments[1] || {});

		var root = {
			id: null,
			parent: null,
			children: [],
			container: element,
			position: 0
		}

		return Sortable._tree(element, options, root);
	},

	/* Construct a [i] index for a particular node */
	_constructIndex: function(node) {
		var index = '';
		do {
			if (node.id) index = '[' + node.position + ']' + index;
		}
		while ((node = node.parent) != null);
		return index;
	},

	sequence: function(element) {
		element = $(element);
		var options = Object.extend(this.options(element), arguments[1] || {});

		return $(this.findElements(element, options) || []).map(function(item) {
			return item.id.match(options.format) ? item.id.match(options.format)[1] : '';
		});
	},

	setSequence: function(element, new_sequence) {
		element = $(element);
		var options = Object.extend(this.options(element), arguments[2] || {});

		var nodeMap = {};
		this.findElements(element, options).each(function(n) {
			if (n.id.match(options.format)) nodeMap[n.id.match(options.format)[1]] = [n, n.parentNode];
			n.parentNode.removeChild(n);
		});

		new_sequence.each(function(ident) {
			var n = nodeMap[ident];
			if (n) {
				n[1].appendChild(n[0]);
				delete nodeMap[ident];
			}
		});
	},

	serialize: function(element) {
		element = $(element);
		var options = Object.extend(Sortable.options(element), arguments[1] || {});
		var name = encodeURIComponent((arguments[1] && arguments[1].name) ? arguments[1].name: element.id);

		if (options.tree) {
			return Sortable.tree(element, arguments[1]).children.map(function(item) {
				return [name + Sortable._constructIndex(item) + "[id]=" + encodeURIComponent(item.id)].concat(item.children.map(arguments.callee));
			}).flatten().join('&');
		} else {
			return Sortable.sequence(element, arguments[1]).map(function(item) {
				return name + "[]=" + encodeURIComponent(item);
			}).join('&');
		}
	}
}

// Returns true if child is contained within element
Element.isParent = function(child, element) {
	if (!child.parentNode || child == element) return false;
	if (child.parentNode == element) return true;
	return Element.isParent(child.parentNode, element);
}

Element.findChildren = function(element, only, recursive, tagName) {
	if (!element.hasChildNodes()) return null;
	tagName = tagName.toUpperCase();
	if (only) only = [only].flatten();
	var elements = [];
	$A(element.childNodes).each(function(e) {
		if (e.tagName && e.tagName.toUpperCase() == tagName && (!only || (Element.classNames(e).detect(function(v) {
			return only.include(v)
		})))) elements.push(e);
		if (recursive) {
			var grandchildren = Element.findChildren(e, only, recursive, tagName);
			if (grandchildren) elements.push(grandchildren);
		}
	});

	return (elements.length > 0 ? elements.flatten() : []);
}

Element.offsetSize = function(element, type) {
	return element['offset' + ((type == 'vertical' || type == 'height') ? 'Height': 'Width')];
}
